diff --git a/src/core-fmt/include/mp-units/format.h b/src/core-fmt/include/mp-units/format.h
index 7929bb2f..dc1f4c15 100644
--- a/src/core-fmt/include/mp-units/format.h
+++ b/src/core-fmt/include/mp-units/format.h
@@ -22,7 +22,7 @@
 
 #pragma once
 
-#include <mp-units/bits/algorithm.h>
+#include <mp-units/bits/external/algorithm.h>
 #include <mp-units/bits/fmt.h>
 #include <mp-units/customization_points.h>
 #include <mp-units/quantity.h>
diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index edfd2331..7159996e 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -31,19 +31,19 @@ endif()
 add_library(
     mp-units-core
     INTERFACE
+    include/mp-units/bits/external/algorithm.h
     include/mp-units/bits/external/fixed_string.h
     include/mp-units/bits/external/hacks.h
+    include/mp-units/bits/external/math_concepts.h
+    include/mp-units/bits/external/prime.h
     include/mp-units/bits/external/type_list.h
     include/mp-units/bits/external/type_name.h
     include/mp-units/bits/external/type_traits.h
-    include/mp-units/bits/algorithm.h
     include/mp-units/bits/dimension_concepts.h
     include/mp-units/bits/expression_template.h
     include/mp-units/bits/get_associated_quantity.h
     include/mp-units/bits/get_common_base.h
     include/mp-units/bits/magnitude.h
-    include/mp-units/bits/math_concepts.h
-    include/mp-units/bits/prime.h
     include/mp-units/bits/quantity_cast.h
     include/mp-units/bits/quantity_concepts.h
     include/mp-units/bits/quantity_point_concepts.h
diff --git a/src/core/include/mp-units/bits/expression_template.h b/src/core/include/mp-units/bits/expression_template.h
index fedbef0c..738f66ac 100644
--- a/src/core/include/mp-units/bits/expression_template.h
+++ b/src/core/include/mp-units/bits/expression_template.h
@@ -22,9 +22,9 @@
 
 #pragma once
 
+#include <mp-units/bits/external/math_concepts.h>
 #include <mp-units/bits/external/type_list.h>
 #include <mp-units/bits/external/type_traits.h>
-#include <mp-units/bits/math_concepts.h>
 #include <mp-units/bits/ratio.h>
 
 namespace mp_units {
diff --git a/src/core/include/mp-units/bits/algorithm.h b/src/core/include/mp-units/bits/external/algorithm.h
similarity index 100%
rename from src/core/include/mp-units/bits/algorithm.h
rename to src/core/include/mp-units/bits/external/algorithm.h
diff --git a/src/core/include/mp-units/bits/external/fixed_string.h b/src/core/include/mp-units/bits/external/fixed_string.h
index 2d0da7ec..22681160 100644
--- a/src/core/include/mp-units/bits/external/fixed_string.h
+++ b/src/core/include/mp-units/bits/external/fixed_string.h
@@ -24,7 +24,7 @@
 
 #include <mp-units/bits/external/hacks.h>  // IWYU pragma: keep
 // TODO use <algorithm> when moved to C++20 modules (parsing takes too long for each translation unit)
-#include <mp-units/bits/algorithm.h>
+#include <mp-units/bits/external/algorithm.h>
 
 // IWYU pragma: begin_exports
 #include <compare>
diff --git a/src/core/include/mp-units/bits/math_concepts.h b/src/core/include/mp-units/bits/external/math_concepts.h
similarity index 100%
rename from src/core/include/mp-units/bits/math_concepts.h
rename to src/core/include/mp-units/bits/external/math_concepts.h
diff --git a/src/core/include/mp-units/bits/prime.h b/src/core/include/mp-units/bits/external/prime.h
similarity index 99%
rename from src/core/include/mp-units/bits/prime.h
rename to src/core/include/mp-units/bits/external/prime.h
index b3365bdc..dbc3e976 100644
--- a/src/core/include/mp-units/bits/prime.h
+++ b/src/core/include/mp-units/bits/external/prime.h
@@ -22,7 +22,7 @@
 
 #pragma once
 
-#include <mp-units/bits/algorithm.h>
+#include <mp-units/bits/external/algorithm.h>
 #include <array>
 #include <cstddef>
 #include <cstdint>
diff --git a/src/core/include/mp-units/bits/magnitude.h b/src/core/include/mp-units/bits/magnitude.h
index 3d9fce46..195fa746 100644
--- a/src/core/include/mp-units/bits/magnitude.h
+++ b/src/core/include/mp-units/bits/magnitude.h
@@ -24,10 +24,10 @@
 
 #include <mp-units/bits/expression_template.h>
 #include <mp-units/bits/external/hacks.h>
+#include <mp-units/bits/external/math_concepts.h>
+#include <mp-units/bits/external/prime.h>
 #include <mp-units/bits/external/type_name.h>
 #include <mp-units/bits/external/type_traits.h>
-#include <mp-units/bits/math_concepts.h>
-#include <mp-units/bits/prime.h>
 #include <mp-units/bits/ratio.h>
 #include <mp-units/bits/symbol_text.h>
 #include <mp-units/bits/text_tools.h>
diff --git a/src/core/include/mp-units/quantity_spec.h b/src/core/include/mp-units/quantity_spec.h
index b85db0cc..e07c73f3 100644
--- a/src/core/include/mp-units/quantity_spec.h
+++ b/src/core/include/mp-units/quantity_spec.h
@@ -22,8 +22,8 @@
 
 #pragma once
 
-#include <mp-units/bits/algorithm.h>
 #include <mp-units/bits/expression_template.h>
+#include <mp-units/bits/external/algorithm.h>
 #include <mp-units/bits/external/type_name.h>
 #include <mp-units/bits/external/type_traits.h>
 #include <mp-units/bits/get_common_base.h>
diff --git a/src/core/include/mp-units/unit.h b/src/core/include/mp-units/unit.h
index 21ab974b..c71a2060 100644
--- a/src/core/include/mp-units/unit.h
+++ b/src/core/include/mp-units/unit.h
@@ -22,8 +22,8 @@
 
 #pragma once
 
-#include <mp-units/bits/algorithm.h>
 #include <mp-units/bits/expression_template.h>
+#include <mp-units/bits/external/algorithm.h>
 #include <mp-units/bits/external/fixed_string.h>
 #include <mp-units/bits/external/type_name.h>
 #include <mp-units/bits/external/type_traits.h>
diff --git a/test/unit_test/static/prime_test.cpp b/test/unit_test/static/prime_test.cpp
index c75f04af..0fd724bd 100644
--- a/test/unit_test/static/prime_test.cpp
+++ b/test/unit_test/static/prime_test.cpp
@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <mp-units/bits/prime.h>
+#include <mp-units/bits/external/prime.h>
 #include <type_traits>
 #include <utility>